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  1. Abstract 3C 186, a radio-loud quasar at z = 1.0685, was previously reported to have both velocity and spatial offsets from its host galaxy, and has been considered as a promising candidate for a gravitational wave recoiling black hole triggered by a black hole merger. Another possible scenario is that 3C 186 is in an ongoing galaxy merger, exhibiting a temporary displacement. In this study, we present analyses of new deep images from the Hubble Space Telescope WFC3-IR and Advanced Camera for Surveys, aiming to characterize the host galaxy and test this alternative scenario. We carefully measure the light-weighted center of the host and reveal a significant spatial offset from the quasar core (11.1 ± 0.1 kpc). The direction of the confirmed offset aligns almost perpendicularly to the radio jet. We do not find evidence of a recent merger, such as a young starburst in disturbed outskirts, but only marginal light concentration in F160W at ∼30 kpc. The host consists of mature (≳200 Myr) stellar populations and one compact star-forming region. We compare with hydrodynamical simulations and find that those observed features are consistently seen in late-stage merger remnants. Taken together, those pieces of evidence indicate that the system ismore »not an ongoing/young merger remnant, suggesting that the recoiling black hole scenario is still a plausible explanation for the puzzling nature of 3C 186.« less
    Free, publicly-accessible full text available June 1, 2023
  2. ABSTRACT We present a catalogue of 22 755 objects with slitless, optical, Hubble Space Telescope (HST) spectroscopy from the Grism Lens-Amplified Survey from Space (GLASS). The data cover ∼220 sq. arcmin to 7-orbit (∼10 ks) depth in 20 parallel pointings of the Advanced Camera for Survey’s G800L grism. The fields are located 6 arcmin away from 10 massive galaxy clusters in the HFF and CLASH footprints. 13 of the fields have ancillary HST imaging from these or other programs to facilitate a large number of applications, from studying metal distributions at z ∼ 0.5, to quasars at z ∼ 4, to the star formation histories of hundreds of galaxies in between. The spectroscopic catalogue has a median redshift of 〈z〉 = 0.60 with a median uncertainty of $\Delta z / (1+z)\lesssim 2{{\ \rm per\ cent}}$ at $F814\mathit{ W}\lesssim 23$ AB. Robust continuum detections reach a magnitude fainter. The 5 σ limiting line flux is $f_{\rm lim}\approx 5\times 10^{-17}\rm ~erg~s^{-1}~cm^{-2}$ and half of all sources have 50 per cent of pixels contaminated at ≲1 per cent. All sources have 1D and 2D spectra, line fluxes/uncertainties and identifications, redshift probability distributions, spectral models, and derived narrow-band emission-line maps from the Grism Redshift and Line Analysis tool (grizli). We provide other basic sample characterizations,more »show data examples, and describe sources and potential investigations of interest. All data and products will be available online along with software to facilitate their use.« less
  3. Abstract We constrain the distribution of spatially offset Lyman-alpha emission (Ly α) relative to rest-frame ultraviolet emission in ∼300 high redshift (3 < z < 5.5) Lyman-break galaxies (LBGs) exhibiting Ly α emission from VANDELS, a VLT/VIMOS slit-spectroscopic survey of the CANDELS Ultra Deep Survey and Chandra Deep Field South fields (≃0.2 deg2 total). Because slit spectroscopy only provides one spatial dimension, we use Bayesian inference to recover the underlying two-dimensional Ly α spatial offset distribution. We model the distribution using a two-dimensional circular Gaussian, defined by a single parameter σr,Ly α, the standard deviation expressed in polar coordinates. Over the entire redshift range of our sample (3 < z < 5.5), we find $\sigma _{r,\mathrm{Ly}\,\alpha }=1.70^{+0.09}_{-0.08}$ kpc ($68\hbox{ per cent}$ conf.), corresponding to ∼0${^{\prime\prime}_{.}}$25 at 〈z〉 = 4.5. We also find that σr,Ly α decreases significantly with redshift. Because Ly α spatial offsets can cause slit losses, the decrease in σr,Ly α with redshift can partially explain the increase in the fraction of Ly α emitters observed in the literature over this same interval, although uncertainties are still too large to reach a strong conclusion. If σr,Ly α continues to decrease into the reionization epoch, then the decrease in Ly α transmission from galaxies observed during this epoch might requiremore »an even higher neutral hydrogen fraction than what is currently inferred. Conversely, if spatial offsets increase with the increasing opacity of the intergalactic medium, slit losses may explain some of the drop in Ly α transmission observed at z > 6. Spatially resolved observations of Ly α and UV continuum at 6 < z < 8 are needed to settle the issue.« less
  4. International Ocean Discovery Program (IODP) Expedition 362T was part of the transit from the April–June 2016 tie up in Cape Town, South Africa, to the IODP Expedition 362 port call in Colombo, Sri Lanka, (4 July–6 August 2016). Hole U1473A remedi- ation operations, approved in March 2016 by the JOIDES Resolution Facility Board (JRFB), took place 12–21 July 2016. The objectives of the Expedition 362T remedial operations were to remove the me- chanical bit release retainer sleeve (MBR-RS) left at the bottom of Hole U1473A at the end of IODP Expedition 360, cement multiple fault zone intervals to stabilize them, obtain a borehole temperature log across the fault zones (at the beginning of operations), and deepen the hole by coring an interval of no more than ~20 m. The planned temperature logging run at the beginning of opera- tions was only partially successful because the logging tool could not be lowered below a ledge at 277 m wireline log depth below sea- floor (WSF). Subsequent reaming using two tricone bit runs estab- lished a clean hole free of debris to the total depth of 789.7 m drilling depth below seafloor (DSF) established during Expedition 360. The fishing run with themore »reverse circulation junk basket (RCJB) yielded a surprise: it deepened Hole U1473A by 0.5 m and no junk was present at the bottom of the hole (i.e., the MBR-RS must have been removed with the last RCJB run during Expedition 360 and fallen to the seafloor without leaving any operational evidence). Next, four coring intervals deepened Hole U1473A by another 19.2 m, recovering 16.55 m (86%). The last task, cementing four fault zones identified in cores and mapped precisely based on Expedition 360 wireline logs, was partly successful. We completely cemented the lowermost fault zone (584–500 m DSF) and partly cemented the second lowest and most intense fault zone (489–443 m DSF). The upper two, less severe fault zones were not cemented at all.« less
  5. This is the site description for U1473 at Atlantis Bank
  6. Expedition reports: core descriptions, maps, data reports
  7. International Ocean Discovery Program (IODP) Expedition 360 was the first leg of Phase I of the SloMo (shorthand for “The nature of the lower crust and Moho at slower spreading ridges”) Project, a multiphase drilling program that proposes to drill through the out- ermost of the global seismic velocity discontinuities, the Mohor- ovičić seismic discontinuity (Moho). The Moho corresponds to a compressional wave velocity increase, typically at ~7 km beneath the oceans, and has generally been regarded as the boundary be- tween crust and mantle. An alternative model, that the Moho is a hydration front in the mantle, has recently gained credence upon the discovery of abundant partially serpentinized peridotite on the seafloor and on the walls of fracture zones, such as at Atlantis Bank, an 11–13 My old elevated oceanic core complex massif adjacent to the Atlantis II Transform on the Southwest Indian Ridge. Hole U1473A was drilled on the summit of Atlantis Bank during Expedition 360, 1–2 km away from two previous Ocean Drilling Program (ODP) holes: Hole 735B (drilled during ODP Leg 118 in 1987 and ODP Leg 176 in 1997) and Hole 1105A (drilled during ODP Leg 179 in 1998). A mantle peridotite/gabbro contact has beenmore »traced by dredging and diving along the transform wall for 40 km. The contact is located at ~4200 m depth on the transform wall be- low the drill sites but shoals considerably 20 km to the south, where it was observed in outcrop at 2563 m depth. Moho reflections, how- ever, have been found at ~5–6 km beneath Atlantis Bank and <4 km beneath the transform wall, leading to the suggestion that the seis- mic discontinuity may not represent the crust/mantle boundary but rather an alteration (serpentinization) front. This in turn raises the interesting possibility that methanogenesis associated with ser- pentinization could support a whole new planetary biosphere deep in the oceanic basement. The SloMo Project seeks to test these hy- potheses at Atlantis Bank and evaluate the processes of natural car- bon sequestration in the lower crust and uppermost mantle. A primary objective of SloMo Leg 1 was to explore the lateral variability of the stratigraphy established in Hole 735B. Comparison of Hole U1473A with Holes 735B and 1105A allows us to demon- strate a continuity of process and complex interplay of magmatic ac- cretion and steady-state detachment faulting over a time period of ~128 ky. Preliminary assessment indicates that these sections of lower crust are constructed by repeated cycles of intrusion, repre- sented in Hole U1473A by approximately three upwardly differenti- ated hundreds of meter–scale bodies of olivine gabbro broadly similar to those encountered in the deeper parts of Hole 735B. Specific aims of Expedition 360 focused on gaining an under- standing of how magmatism and tectonism interact in accommo- dating seafloor spreading, how magnetic reversal boundaries are expressed in the lower crust, assessing the role of the lower crust and shallow mantle in the global carbon cycle, and constraining the extent and nature of life at deep levels within the ocean lithosphere.« less
  8. During the 11 day transit from Colombo, Sri Lanka, to International Ocean Discovery Program (IODP) Site U1473 at Atlantis Bank, the Expedition 360 science party reexamined cores drilled during Ocean Drilling Program (ODP) Leg 179 in Hole 1105A (Pettigrew, Casey, Miller, et al., 1999; Casey et al., 2007). This activity involved rigorously describing the cores and many of the accompanying thin sections with the primary purpose of familiarizing the science party with the material likely to be encountered at the new Site U1473, situated 1.4 km to the north. The science party developed templates for description of the igneous, metamorphic, and structural features of the cores and analyzed thin sections made during Leg 179 to establish core description protocols for the new Site U1473 cores. An additional benefit of redescribing Hole 1105A cores is that the data generated are in a format directly comparable with those for Hole U1473A. In general, our findings were very similar to those produced by the Leg 179 scientists; however, with a larger science party to work on the cores, some of the information collected is new. We include this information in this chapter, as a basis for direct comparison with the results of drillingmore »at Site U1473. In addition, we were able to make certain physical properties measurements on Hole 1105A cores, including magnetic susceptibility measurements of core section halves, that had not been possible during Leg 179. It is important to note here that the observations made on Hole 1105A cores by the Expedition 360 science party augment rather than replace those made by the Leg 179 scientists.« less
  9. International Ocean Discovery Program (IODP) Expedition 360 was the first leg of Phase I of the SloMo (shorthand for “The nature of the lower crust and Moho at slower spreading ridges”) Project, a multiphase drilling program that proposes to drill through the outermost of the global seismic velocity discontinuities, the Mohorovičić seismic discontinuity (Moho). The Moho corresponds to a compressional wave velocity increase, typically at ~7 km beneath the oceans, and has generally been regarded as the boundary between crust and mantle. An alternative model, that the Moho is a hydration front in the mantle, has recently gained credence upon the discovery of abundant partially serpentinized peridotite on the seafloor and on the walls of fracture zones, such as at Atlantis Bank, an 11–13 My old elevated oceanic core complex massif adjacent to the Atlantis II Transform on the Southwest Indian Ridge. Hole U1473A was drilled on the summit of Atlantis Bank during IODP Expedition 360, 1–2 km away from two previous Ocean Drilling Program (ODP) holes: Hole 735B (drilled during ODP Leg 118 in 1987 and ODP Leg 176 in 1997) and Hole 1105A (drilled during ODP Leg 179 in 1998). A mantle peridotite/gabbro contact has been traced bymore »dredging and diving along the transform wall for 40 km. The contact is located at ~4200 m depth at the drill sites but shoals considerably 20 km to the south, where it was observed in outcrop at 2563 m depth. Moho reflections have, however, been found at ~5–6 km beneath Atlantis Bank and <4 km beneath the transform wall, leading to the suggestion that the seismic discontinuity may not represent the crust/mantle boundary but rather an alteration (serpentinization) front. This then raises the interesting possibility that a whole new planetary biosphere may thrive due to methanogenesis associated with serpentinization. The SloMo Project seeks to test these two hypotheses at Atlantis Bank and evaluate carbon sequestration in the lower crust and uppermost mantle. A primary objective of SloMo Leg 1 was to explore the lateral variability of the stratigraphy established in Hole 735B. Comparison of Hole U1473A with Holes 735B and 1105A allows us to demonstrate a continuity of process and complex interplay of magmatic accretion and steady-state detachment faulting over a time period of ~128 ky. Preliminary assessment indicates that these sections of lower crust are constructed by repeated cycles of intrusion, represented in Hole U1473A by approximately three upwardly differentiated hundreds of meter–scale bodies of olivine gabbro broadly similar to those encountered in the deeper parts of Hole 735B. Specific aims of Expedition 360 focused on gaining an understanding of how magmatism and tectonism interact in accommodating seafloor spreading, how magnetic reversal boundaries are expressed in the lower crust, assessing the role of the lower crust and shallow mantle in the global carbon cycle, and constraining the extent and nature of life at deep levels within the ocean lithosphere.« less